Freshwater Snail Biomphalaria Glabrata Research Articles

Microsatellite variation in the freshwater schistosome-transmitting snail Biomphalaria glabrata.

Microsatellite variation in the freshwater schistosome-transmitting snail Biomphalaria glabrata.

Monoamines and their metabolites in the freshwater snail Biomphalariaglabrata

Metabolism of the major monoamines and their functions were studied in the freshwater snail Biomphalaria glabrata. In both juvenile and adult snails, the plasma (cell-free hemolymph) appears to act as a reservoir for most of these monoamines and their metabolites including among others, l-dopa and dopamine as major constituents. Significant quantities of l-tryptophan, precursor of indoleamines, also was found in the plasma. l-dopa, serotonin, homovanillic acid and dopamine were prominently represented in the central nervous system of the snail, while serotonin and its metabolites, 5-hydroxyindole acetic acid and 5-hydroxytryptophol were found in the ovotestis. Catecholamines such as l-dopa, dopamine and homovanillic acid were identified in the albumen gland. Functional aspects of both dopamine and serotonin were studied using in vitro cultures of albumen glands, the site of perivitelline fluid and galactogen synthesis in B. glabrata. Dopamine was found to stimulate the release of secretory proteins when exogenously added to gland cultures and this process was inhibited by chlorpromazine, a dopamine receptor antagonist. Similarly, exogenous serotonin stimulated in vitro protein secretion by albumen glands. Thus, these results suggest that monoamines may play important roles in regulating reproductive activity of this snail and provides an excellent model for studying neurotransmitter function and metabolism in molluscs.

Glycosidase activities in plasma of naive and schistosome-infected Biomphalaria glabrata (Gastropoda).

Activity of the following glycosidases was detected in the plasma of the freshwater snail Biomphalaria glabrata: beta-D-fucosidase, beta-D-glucosidase, beta-D-galactosidase, beta-D-mannosidase, beta-D-glucuronidase, N-acetyl-beta-D-galactosaminidase, N-acetyl-beta-D-glucosaminidase, and lysozyme. At the physiological pH (7.2-7.4) of snail haemolymph, enzymatic activity was about 10-50% of the maximum activity at each enzyme's respective acid pH-optimum. Schistosome-susceptible B. glabrata showed lower plasma protein concentration and significantly lower enzymatic activities (U/mg protein) than schistosome-resistant snails. Changes in glycosidase activity levels correlate with the progress of infection. After successful schistosome invasion, activities of plasma glycosidases but not the concentration of total plasma proteins increased significantly during the first 2 days in both snail strains. Thus, most tegumental glycoproteins of schistosome larvae can be altered by humoral host glycosidases. The detection of only very low activities of hexosaminidases leads to the hypothesis that GalNAc/GlcNAc may be involved in the process of non-self recognition. At 4 days post-infection, glycosidase activities were identical or slightly below the levels found in naive snails. At this time of infection the parasite is encapsulated and destroyed by haemocytes of resistant snails. In susceptible snails, however, the schistosomes have transformed into sporocysts and will complete their life-cycle without eliciting effective defence reactions. After > 30 days post-infection, when cercariae are fully developed in susceptible snails, plasma protein concentration decreased significantly, whereas glycosidase activities were elevated.

Carbohydrates of the Organic Shell Matrix and the Shell-Forming Tissue of the Snail Biomphalaria glabrata (Say).

Sulfated carbohydrates may play a role in the biomineralization of the molluscan shell. The carbohydrates of the extracted water-insoluble organic shell matrix (IM) of the freshwater snail Biomphalaria glabrata were identified as glucose, mannose, galactose, and N-acetyl-glucosamine, whereas the water-soluble organic matrix (SM) additionally contained N-acetyl-galactosamine. A specific lectin binding pattern of the matrix was obtained. One prominent protein of the SM, with a size of 19.6 kDa and a pI of 7.4, was shown to be a glycoprotein with terminal glucosyl or mannosyl moieties. The acidic constitutents of the matrix showed a variety of possible terminal sugars, indicating a heterogenous mixture of proteoglycans or glycosaminoglycans (GAGs) and glycoproteins. At the shell-forming mantle edge, an alcian-blue-positive material was observed in the periostracum groove (PG), the belt, and apically in the cells of the outer mantle epithelium (OME). With the help of lectins, all sugars in question were detected in the PG and the belt, whereas the OME was bound by glucose/mannose- and GlcNac-specific lectins only. Although the complete set of GAGs will be produced in the PG and the belt, a very acidic fraction of GAGs and the 19.6-kDa protein can also be delivered by the OME.

The Organic Shell Matrix of the Freshwater Snail Biomphalaria glabrata

The organic matrix of the aragonitic, cross-lamellar-structured shell of the freshwater snail Biomphalaria glabrata (Basommatophora, Pulmonata) has been investigated. The analysis of the water-soluble matrix components revealed protein as the main part of the matrix, followed by sulfate, neutral sugar, amino sugar, and small amounts of uronic acid and phosphate. In the amino acid analysis, glycine was the main amino acid of all matrix fractions. In the water-soluble matrix, potentially acidic amino acids did not exceed 23%, while hydrophobic amino acids reached 37%. The SDS-electrophoretical separation gave a very prominent band at 19.6 kDa and several weaker bands of higher molecular weight. The 19.6 kDa protein had a pI of 7.4, and at the N-terminus a high amount of hydrophobic amino acids were found. Additionally, the organic matrix consists to a considerable amount of glycosaminoglycans or proteoglycanes of undetermined size. These Alcian Blue- and Stains-all-positive matrix constituents could be involved in the accumulation of calcium in the shell.

Development of the statocyst in the freshwater snail Biomphalaria glabrata (Pulmonata, Basommatophora)

The development of the statocyst of the freshwater snail Biomphalaria glabrata has been examined from embryo to adult. Special emphasis was put on the growth of the statoconia in the statocysts. In the statocysts of embryonic snails (90–120 h after oviposition) there is not a single statolith but an average of 40–50 statoconia per statocyst. The number of statoconia increases to 385–400 when the snails reach a shell diameter of 4 mm and remains relatively constant thereafter, irrespective of shell size. Small statoconia are found in supporting cells, which suggests that the statoconia are produced within these cells. The average diameter of statoconia and the total mass of statoconia increase with increasing shell diameter. The average number of large statoconia (diameter >7 μm) per statocyst continues to increase from 2 to 10 mm animals while the number of small ones (diameter <4 μm) initially rises and then decreases after 4 mm. These results demonstrate continuous growth of the statoconia in the cyst lumen of Biomphalaria. The single statoconia vibrate in a regular pattern in vivo, indicating beating of the statocyst cilia. The statoconia sink under the influence of gravity to load and stimulate receptor cells which are at the bottom. The length of cilia and the size of statocyst gradually increase as the animal grows. However, the increase in the volume of the statocyst is relatively small compared with the increase in body weight during normal development.

The structure of the statocyst of the freshwater snail Biomphalaria glabrata (Pulmonata, Basommatophora)

The structure of the statocyst of the freshwater snail Biomphalaria glabrata has been examined by light and electron microscopy. The two statocysts are located on the dorsal-lateral side of the left and right pedal ganglion. The statocysts are spherical, fluid-filled capsules with a diameter of approximately 60 μm for young and 110 μm for adult snails. The wall of the cyst is composed of large receptor cells and many smaller supporting cells. The receptor cells bear cilia which are evenly distributed on the apical surface. The cilia have the typical 9+2 internal tubule configuration. Striate rootlets originate from the base of the basal body and run downward into the cytoplasm. Side-roots arise from one side of the basal body and a basal foot from the other. For each receptor cell, the basal foot always points to the periphery of the surface, indicating that the receptor cell is non-polarized. The receptor cells contain cytoplasmic organelles such as mitochondria, ribosomes, rough and smooth endoplasmic reticulum, compact Golgi bodies and multivesicular bodies. Supporting cells bearing microvilli are interposed between the receptor cells. The junction complex between the supporting cells and the receptor cells is composed of adherens and septate junctions, while between supporting cells only the adherens junctions are present. The static nerve arises from the lateral side of the cyst and contains axons in which parallel neurotubules and mitochondria are found. The axons arise directly from the base of the receptor cells without synapse. In the cyst lumen there are unattached statoconia. The statoconia have a plate-like or concentric membranous ring structure. Based on the morphology, the function of the statocyst in Biomphalaria is discussed.

Detection and partial characterization of glycosidases in the hemolymph of Biomphalaria glabrata (Gastropoda)

Glycosidases modify, degrade and regulate glycoconjugates and are possibly involved in nutrition as well as in inflammation and humoral defense reactions in invertebrates. In this study, hemolymph from the freshwater snail Biomphalaria glabrata has been analyzed for its content of serum glycosidases by photometric assays and after protein separation by native-polyacrylamide gel electrophoresis and isolectric focusing. Activity of β- d-fucosidase, β- d-galactosidase, β- d-glucosidase, β- d-mannosidase, β- d-glucuronidase, N-acetyl-β- d-galactosaminidase, N-acetyl-β- d-glucosaminidase and lysozyme was detected. Highest enzyme activity corresponds to β- d-fucosidase followed by β- d-glucosidase > β- d-galactosidase > β- d-mannosidase > lysozyme > glucuronidase > hexosaminidase(s). Enzymes are active in the range of pH values between 3.5 and 7.5. The pH optima of the enzymes are between pH 3.5 and 6.5 (β- d-glucuronidase, N-acetyl-β- d-hexosaminidase(s):pH 3.5; lysozyme: pH 5.0; β- d-mannosidase: pH 5.5; β- d-fucosidase, β- d-galactosidase, β- d-glucosidase: pH 5.5–6.5). Molecular weights of native enzymes are between 90 and 460 kDa (β- d-glucuronidase, 430–460 kDa; β- d-fucosidase, β- d-galactosidase, α/β- d-glucosidase, 290–320 and 330–380 kDa; N-acetyl-β- d-hexosaminidase(s), 220–280 kDa; β- d-mannosidase, 185–290 kDa; α- d-mannosidase; 90–100 kDa).

Glucose transport across the intestinal wall of the freshwater snail Biomphalaria glabrata

1. 1. Isolated midguts of the freshwater snail Biomphalaria glabrata were mounted in an incubation chamber in saline containing 2 mM glucose and perfused with the same solution. External and internal media were continuously gassed with carbogen gas (95% O 2, 5% CO 2). In order to measure the flux rates of glucose [ 14C]glucose was applied in the perfusion medium or in the incubation medium. Net fluxes of glucose were calculated as the differences between unidirectional in- and effluxes. 2. 2. A directed net flux from the mucosal to the serosal side of the intestine was demonstrated (mucosal to serosal = 50 ± 10 nmol cm −2hr −1( N = 6) serosal to mucosal 7 ± 1 nmol cm −2hr −1 ( N = 6), net flux = 43 nmol cm −2hr −1).r 3. 3. The active transport of glucose was reduced by the presence of metabolic inhibitors, cyanide (1 mM) and dinitrophenol (1 mM) on the mucosal as well as on the serosal side. Ouabain (1 mM) inhibited the transport rate only when it was added on the serosal side. Amiloride (1 mM) had no effect on the transport rate whether added on the mucosal or on the serosal side. 4. 4. Inhibition of glucose transport by oubain, a specific inhibitor of Na +/K +-ATPase, suggests that glucose transport is secondary active and coupled to Na +-transport.

Lysozyme activity in the cephalochordate Branchiostoma lanceolatum

Glycosidases modify, degrade and regulate glycoconjugates and are possibly involved in nutrition as well as in inflammation and humoral defense reactions in invertebrates. In this study, hemolymph from the freshwater snail Biomphalaria glabrata has been analyzed for its content of serum glycosidases by photometric assays and after protein separation by native-polyacrylamide gel electrophoresis and isolectric focusing. Activity of β-d-fucosidase, β-d-galactosidase, β-d-glucosidase, β-d-mannosidase, β-d-glucuronidase, N-acetyl-β-d-galactosaminidase, N-acetyl-β-d-glucosaminidase and lysozyme was detected. Highest enzyme activity corresponds to β-d-fucosidase followed by β-d-glucosidase > β-d-galactosidase > β-d-mannosidase > lysozyme > glucuronidase > hexosaminidase(s). Enzymes are active in the range of pH values between 3.5 and 7.5. The pH optima of the enzymes are between pH 3.5 and 6.5 (β-d-glucuronidase, N-acetyl-β-d-hexosaminidase(s):pH 3.5; lysozyme: pH 5.0; β-d-mannosidase: pH 5.5; β-d-fucosidase, β-d-galactosidase, β-d-glucosidase: pH 5.5–6.5). Molecular weights of native enzymes are between 90 and 460 kDa (β-d-glucuronidase, 430–460 kDa; β-d-fucosidase, β-d-galactosidase, α/β-d-glucosidase, 290–320 and 330–380 kDa; N-acetyl-β-d-hexosaminidase(s), 220–280 kDa; β-d-mannosidase, 185–290 kDa; α-d-mannosidase; 90–100 kDa).

Immunosuppression in the definitive and intermediate hosts of the human parasite Schistosoma mansoni by release of immunoactive neuropeptides.

Evidence supporting the concept that the parasitic trematode Schistosoma mansoni may escape immune reactions from its vertebrate (man) or invertebrate (the freshwater snail Biomphalaria glabrata) hosts by using signal molecules it has in common with these hosts was obtained by the following experiments. The presence of immunoactive proopiomelanocortin (POMC)-derived peptides [corticotropin (ACTH), beta-endorphin] in, and their release from, S. mansoni was demonstrated. Coincubation of adult worms with human polymorphonuclear leukocytes or B. glabrata immunocytes led to the appearance of alpha-melanotropin (MSH) in the medium. The conclusion that this alpha-MSH resulted from conversion of the parasite ACTH by neutral endopeptidase 24.11 (NEP) present on these cells was supported by the fact that the alpha-MSH level in the medium was markedly reduced by addition of the specific NEP inhibitor phosphoramidon. This interpretation is substantiated by the fact that no conversion was observed in comparable tests with human monocytes, which exhibit no NEP activity. alpha-MSH has the capacity to inactivate formerly active immunocytes not only from the definitive host (man, hamster) but also from the intermediate host (B. glabrata), as determined by microscopic computer-assisted examination of conformational changes. POMC-derived peptides have been detected in B. glabrata hemolymph 2, 10, and 24 days after infection by S. mansoni miracidia. Immunocytes from infected snails were found to be inactivated, and this inactivation was prevented by antibodies directed against ACTH and alpha-MSH. The immunoactive beta-endorphin released from S. mansoni does not appear to be subject to enzymatic conversion. Since it is active at lower concentrations, it may be used for distant signaling.

Embryonic development of the shell in biomphalaria glabrata (Say).

During embryogenesis of the fresh water snail Biomphalaria glabrata (Say) (Pulmonata, Basommatophora) shell formation has been studied by light and electron microscopical techniques. The shell field invagination (SFI), the secretion of the first shell layers, the development of the shell-forming mantle edge gland and spindle formation have been investigated. During embryonic development at 28 degrees C environmental temperature, the shell field invaginates after 35 h. After 40 h the SFI is closed apically by cellular protrusions and scale-like precursors of the periostracum. The first electron translucent layer of the periostracum stems from electron dense vesicles of the cells which lie at the opening of the SFI. A second electron dense layer appears some hours afterwards. When the shell appears birefringent in the polarizing microscope (45 h of development) calcium can be detected in it using energy dispersive x-ray analysis. As calcification occurs the intercrystalline matrix appears under the periostracum and the SFI begins to open. In embryos of 60 h the mantle cavity appears at the left caudal side. When the mantle edge groove develops (65 h of development) lamellate units are added to the outer layer of the periostracum, but no distinct lamellar layer is formed in B. glabrata. In addition to the lamellar cell and the periostracum cell, a secretory cell can be observed in the developing groove. After 65 h of development, spindle formation starts and the shell begins to coil in a left hand spiral. After 5 days of development the embryos are ready to leave the egg capsules.

Comparative glucose tolerance studies in the freshwater snail Biomphalaria glabrata: influence of starvation and infection with the trematode Schistosoma mansoni

The dynamic reactions of B. glabrata on intravasal loads of 20-1000 micrograms glucose.g live fresh wt-1 were studied in standard fed snails (SFS). Starved snails (SS) and snails infected with S. mansoni (IS) were given 100-500 micrograms glucose.g fresh live wt-1. Mean hemolymph glucose level was 12.1 mg.100 ml-1 in SFS. It was not significantly lower in SS (10.7 mg.100 ml-1), but significantly reduced in IS (8.5 mg.100 ml-1). Since hemolymph volumes were significantly increased in SS, the amount of circulating glucose (pool) did not change (75 micrograms.g body weight-1) compared to SFS (62 micrograms.g-1). It was, however, reduced to 41 micrograms.g-1 in IS. In SFS the circulating glucose pool had to be doubled to induce significantly elimination of the injected glucose. Tripled pools were eliminated with half-times of 45 min, whereas lower and higher glucose loads were eliminated significantly slower (half-times: 80-105 min). Glucose tolerance of SS was reduced: half-times were doubled, and metabolization of injected glucose was reduced. Since tissue fresh weights were lowered by 40%, absolute incorporation of 14C from labeled glucose was lowered, but specific incorporation (per mg) was higher than in SFS and IS. Glucose tolerance of IS was increased: metabolic clearance rates rose by 70% and half-times were shortened by 30%, though absolute and specific rates of 14C incorporation were lowered. However, IS lost 25% of the label to the water, whereas SFS lost 12% and SS only lost 8%. Using the antimetabolite 2-deoxyglucose, 80% of the losses proved to be glucose in IS, and 50% in SFS. The present results suggest the existence of a glucostatic regulation in B. glabrata with lower sensitivity and capacity than in mammals. As to glucose tolerance, the often reported parallelism in metabolic shifts induced by starvation and parasitic infection was not confirmed.

Relationship between light conditions and behavior of the freshwater snail Biomphalaria glabrata (Say)

The influence of light upon behavior of Biomphalaria glabrata was investigated in snails submitted for 48 h to one of the following regimes: normal light cycle, continuous darkness, continuous light. Time-lapse cinematography was used to provide data about snail locomotor activity in response to (a) continuous light or darkness; (b) light or dark phases; (c) light transitions. Snails were significantly less active under continuous light than under continuous or intermittent darkness. Under the normal light cycle, the activity rate was significantly higher in the dark than in the light. Changes from light to dark corresponded to increases in the activity rate which persisted long afterwards. No significant variation in activity occurred upon changes from dark to light.

The biochemical ecology of Biomphalaria glabrata, a snail host of Scistosoma mansoni: Short chain carboxylic and amino acids as phagostimulants

1. 1. A buccal mass olfactometer was used to investigate the responses of the fresh-water pulmonate snail Biomphalaria glabrata to carboxylic and amino acids. 2. 2. The snails proved very discriminating as only 6 (14.6%) of the 41 chemical species tested were effective as phagostimulants. These are ranked as follows in order of potency:- butanoate > propanoate > d-malate >2-hydroxybutanoate = l-tartrate = l-aspartate. 3. 3. The structure-activity relationships of the active compounds, and their significance to the ecology and control of the snails are discussed.

The effect of low zinc concentrations on some demographic parameters of Biomphalaria glabrata (Say), mollusca: gastropoda

The effects of low zinc concentrations on the freshwater snail Biomphalaria glabrata (Say) were measured under continuous flow conditions. The time of sexual maturity of young snails, the fecundity and fertility of the adults and the mortality and growth-rate of both stages were investigated. Embryos and snails were exposed to zinc concentrations ranging from 500 ppb to >5000 ppb. The mortality of embryos and young and adult animals rose with increasing zinc concentration. Thirty-three days after the experiment was started, 20% of the adults and 60% of the young individuals died in 1500 ppb Zn 2+, whereas in the control all the animals survived. Embryos did not hatch in 1000 ppb Zn 2+. Fecundity was significantly lowered by 500 and 1500 ppb Zn 2+ and completely suppressed by 3000 ppb. Fertility was lowered by 500 ppb Zn 2+ and the embryos showed a decreasing hatch-rate during the time of experimentation. In respect to the control, 500 ppb Zn 2+ reduced the growth-rate of adult and young animals to about 50%. At 500 ppb sexual maturity was delayed for about 7 days. Higher concentrations prevented growth and the attainment of sexual maturity.

Biomphalaria glabrata (say), a suitable organism for a biotest

The embryonic development of a tropical freshwater snail (Biomphalaria glabrata, Say: Gastropoda, Pulmonata) is presented as a tool for monitoring pollutants in water. Laboratory rearing of the ani...

Laboratory studies on the desiccation of immature stages of the freshwater snail Biomphalaria glabrata.

Dans les habitats naturels B.g. peut etre expose a la dessication, la resistance de quelques specimens est considerable. La survie est influencee a une humidite relative mais le taux precis est rarement determine. Cet article donne quelques informations sur les effets au laboratoire de differents degres d'humidite relative sur les gasteropodes immatures

The chemical ecology of Biomphalaria glabrata (say): Sugars as attractants and arrestants

1. 1. The behavioural responses of the freshwater snail Biomphalaria glabrata to chemical gradients of sugars were investigated by means of diffusion olfactometers. 2. 2. The snails proved very discriminating in their responses. Thus, only nine (39.1%) of the 23 sugars tested proved to be statistically significant attractants or arrestants. None proved to be statistically significant repellents. 3. 3. Of all the sugars tested maltose proved to be the most potent attractant or arrestant. The lower threshold of response to this sugar lies between 5 × 10 −6 and 5 × 10 −7M. 4. 4. The results are compared with those obtained for amino and carboxylic acids and their ecological relevance is discussed.

The chemical ecology of Biomphalaria glabrata (say): Sugars as phagostimulants

1. 1. The buccal-mass responses of the freshwater snail Biomphalaria glabrata to sugars were investigated by means of an olfactometer. 2. 2. The snails proved very discriminating in their responses. Adults responded significantly to only five (12.2%) of the 41 sugars tested at 10 −2 M. Juvenile conspecifics had a broader niche as they responded to eight (47%) of the 17 sugars tested. 3. 3. Of all the sugars tested, maltose proved to be the most potent phagostimulant. 4. 4. The possible mechanisms involved in the chemoreception of active sugars and the ecological relevance of the responses shown by the snails to them are discussed.